There has been introduced a fingerprint authentication apparatus that includes a single fingerprint sensor to receive user's fingerprint data and authenticates a user by comparing the received user's fingerprint data with a previously registered fingerprint data.
In the case of use of a single fingerprint sensor, it is determined that a user is successfully authenticated when a calculation result of a similarity between input fingerprint data and previously registered fingerprint data is greater than a predefined threshold. That is, fingerprint data acquired by a variety of methods, for example, extracting feature points of a fingerprint using a fingerprint sensor, is compared to previously registered fingerprint data, and when the similarity therebetween is greater than, for example, 95%, it is determined that the user authentication is successful. In this case, the threshold is 0.95.
Hence, the authentication result may vary according to a threshold. For example, in a case in which a calculated similarity is 0.96, if a threshold is 0.95, it is determined that the user authentication is successful, whereas, if a threshold is 0.98, it is determined that the user authentication fails. In other words, a threshold defined too large may result in an authentication failure error even when a right user's fingerprint has been input. On the other hand, a threshold defined too small may result in an error of authenticating a wrong user with a wrong fingerprint. A rate of authentication failure with respect to a correct user fingerprint may be referred to as a false rejection rate (FRR), and a rate of false authentication for a wrong user fingerprint may be referred to as a false acceptance rate (FAR).
As such, since the single fingerprint sensor allows only one threshold to be used in authentication process, if the threshold is high, the FAR is lowered and the FRR is raised, and otherwise, if the threshold is low, the FAR is raised and the FRR is lowered. Thus, the performance of the fingerprint authentication apparatus and the occurrence of error may depend on a threshold.